Prior art paint booths are well known. A typical prior art paint booth, used to paint the exterior surfaces of vehicle bodies in both continuous conveyance and stop station systems, includes an enclosure housing a plurality of painting and opener robots disposed on a periphery thereof. These robots can be mounted on the floor, the wall or rails. The painting robots carry either spray guns or rotary applicators (bell machines) for directing atomized paint toward the vehicle body.
A newly manufactured automobile body is typically painted with the doors installed. During the painting process, the doors are moved from a closed position to an open position to facilitate the painting of an interior of the automobile body. The doors are returned to the closed position when the painting of the interior of the automobile body is completed. Opener robots featuring a specially adapted tool disposed at the end of an articulated arm are typically employed to grip and move the doors during the opening and closing process. The automobile hood and tailgate/trunk lid can also be installed on the automobile body and must also be opened and closed during the painting process, similar to the doors.
The prior art painting and opener robots are inherently very costly and limit visual access to the booth. For example, prior art floor-mounted robots require significant booth modification when installed in existing paint booths, increasing installation time and cost, and require more booth length and width. Floor-mounted robots also require frequent cleaning due to the down draft of paint overspray causing paint accumulation on the robot arm and base, which results in higher maintenance and cleaning costs. Furthermore, additional robot zones are often required because one painting robot is unable to reach substantially all paintable surfaces on one side of the article and one opener is unable to reach all of the areas to be opened and, therefore, they lack any backup capability for an inoperative robot. If one robot is inoperative, the entire paint booth is inoperative, causing delays and downtime costs.
The prior art floor-mounted robots also lack flexibility. The lack of flexibility is often a result of the prior art floor-mounted robots having robot arms that are segmented to rotate about only six distinct axes of rotation. The end-effector tools disposed at a terminal end of these six axis robots may only be capable of reaching certain positions and orientations within the job envelope using a limited number of configurations of the segments of the robot arm, and in many cases only one configuration allows the end-effector tool to reach a specified position and configuration. These limited configurations may be problematic if a desired position and orientation of the end-effector tool leads to the prior art six axis robots interfering with other robots or components included within the paint booth. To cure this lack of flexibility, many prior art paint booths add an additional degree of freedom to the six axis robots by placing them on a linear rail system. These rail systems may be excessively expensive and space limiting. Prior art rail-mounted robots also require a rail along which the robots can travel to track a moving conveyor. The rail axis of the robot requires doors at each end of the booth. The waist axis of the robot requires additional safety zone(s) at the ends of the spray booth and the rail cabinets of the floor mounted robots encroach into aisle space and add significant cost.
It is desirable, therefore, to provide a painting apparatus and a painting system that utilizes robots in an efficient and cost-effective manner, minimizes paint waste, occupies little space (length and width) in the paint booth, and can be installed in existing paint booths without requiring significant booth modification.
An improvement on the above-described painting systems is disclosed in the U.S. Pat. No. 7,650,852. This patent describes an apparatus for painting objects including an elevated tubular frame rail mounting a four axis robot arm with a paint applicator. The robot is attached to a mounting base that moves along the rail permitting painting of the top and/or side of a vehicle body. Electrical power and fluid lines can be routed through the rail to the robot. Two such rails and multiple robots can be combined as a module for installation in a new or an existing painting booth.
However, there still is a desire to reduce the size of the paint booth even more by eliminating the need for a linear rail system to translate the robots to a desired position and orientation.